1. Technical Field
The invention relates to a liquid crystal panel, particularly, to a liquid crystal panel suitable for a driving system according to a fringe field switching (FFS) mode.
2. Background Art
A liquid crystal panel has features of lighter weight, a flat-panel and lower electric power consumption in comparison with a cathode ray tube (CRT), and therefore is used for many electronics as a display use.
According to the liquid crystal panel, orientation of liquid crystal molecules aligned in a predetermined direction is changed by an electric field to change an amount of light transmitted through a liquid crystal layer, thereby displaying an image.
The liquid crystal panel includes a reflective type in which outside light enters the liquid crystal layer to be reflected on a reflector, and reflected light re-transmits the liquid crystal layer and is emitted, a transmissive type in which incident light from a backlight apparatus transmits the liquid crystal layer, and a transflective type having both properties.
Moreover, specific methods for applying the electric field to the liquid crystal layer of the liquid crystal panel include a longitudinal electric field system and a transverse electric field system.
In the liquid crystal panel according to the longitudinal electric field system, an electric field substantially in a longitudinal direction is applied to liquid crystal molecules by means of a pair of electrodes arranged by interposing the liquid crystal layer. As the liquid crystal panel according to the longitudinal electric field system, a liquid crystal panel having a mode such as a twisted nematic (TN) mode, a vertical alignment (VA) mode and a multi-domain vertical alignment (MVA) mode is known.
In the liquid crystal panel according to the transverse electric field system, a pair of electrodes is mutually insulated and arranged on an inner surface side of one of substrates of a pair of substrates arranged by interposing the liquid crystal layer, and an electric field substantially in a transverse direction is applied to the liquid crystal molecules. As the liquid crystal panel according to the transverse electric field system, a liquid crystal panel having an in-plane switching (IPS) mode in which a pair of electrodes does not overlap in a planar view, and a fringe field switching (FFS) mode in which a pair of electrodes overlaps in the planar view are known.
The liquid crystal panel according to the transverse electric field system allows obtaining of a wide viewing angle, and therefore has been increasingly used in recent years.
So far, according to a liquid crystal display apparatus having upper and lower substrates to be driven by the FFS mode, in a pixel electrode and a counter electrode being a pair of electrodes arranged in one substrate, even when off-state voltage corresponding to 0 V is applied to a certain pixel, other pixels are turned on, and therefore a specific signal is continuously applied to a data bus line.
Accordingly, a noise field is formed between the data bus line and the pixel electrode or between the data bus line and the counter electrode, thereby liquid crystal molecule isolating from a polarization axis to cause light leakage in the part.
In order to block the leaked light, patterning of a black matrix in a large region is performed to the other substrate, which requires patterning and also induces a decrease of an opening ratio in the liquid crystal panel, and thus a problem resulting in reduction of brightness has been caused.
In order to solve such a problem, Patent literature No. 1 below discloses an art in which, in a liquid crystal display apparatus driven by an IPS mode or an FFS mode being a normally black mode, a rubbing direction of a liquid crystal having a positive dielectric anisotropy (Δ∈) is adjusted to coincide with a direction of a noise field, resulting in allowing a major axis of liquid crystal molecules to precisely coincide with the direction of the noise field, and thus even if the noise field acts, the liquid crystal molecules are not isolated from the polarization axis of a polarizer, and a dark state is designed to be maintained at any time.
Moreover, Patent literature No. 2 below discloses an art in which, in a transflective liquid crystal display apparatus such as an FFS mode liquid crystal display apparatus, a reflection display unit and a transmission display unit are adjusted in twist alignment and homogeneous alignment during no voltage application, and thus a less colored black display having high contrast is designed to be secured.